1. Field of the Invention
The present invention relates to a carriage for an endless conveyor and to a conveying mechanism for such a carriage.
2. Description of the Related Art
An endless conveyor is used in a production line to process work that is being circulated from one station to another. The endless conveyor includes carriages that circulate from one station to another along a conveyance path that is oblong in plan view. The endless conveyor further includes a driving unit for circulating the carriages along the conveyance path. The driving unit has a pair of sprockets and a driving source for driving one of the sprockets. An endless chain is mounted between the sprockets, and the carriages are connected with the chain. The chain conventionally has been provided with joints at specified intervals and the respective carriages are provided with coupling members that can be coupled with the joint.
Many kinds of products often are produced on a single production line. For example, to produce automotive wiring harnesses, it is necessary to set specifications individually according to the lengths of wires of the wiring harnesses, the number of connectors, the number of contacts of the connectors, etc. Some production modes require several kinds of wiring harnesses to be produced simultaneously in one production line. Accordingly, it is sometimes necessary to change the setting of the stations and to change the conveyance paths as a vehicle type and product number are changed, or as the quantity of production is increased or decreased. In these cases, frequent changes to the length of the chain are necessary. Frequent connections and disconnections between the coupling members of the carriages and the joints of the chain also are required in the prior art conveyor that has a plurality of carriages coupled with the joints of the endless chain. Considerable time and labor is required to change the specification and the setup, and, as a result, productivity is poor. Accordingly, there has been an increasing demand in recent years to facilitate changing the number of stations in a production line.
In view of the above, an object of the present invention is to provide a carriage for an endless conveyor in which the specification can be changed easily. Another object of the invention is to provide a conveying mechanism for such a carriage.
The subject invention is directed to a carriage for an endless conveyor that has an endless conveyance path. The conveyance path is comprised of at least two substantially linear paths and turning paths connecting the opposite ends of the substantially linear paths. Carriages are driven by a driving unit of the conveyor to circulate along the conveyance path in a predetermined conveyance direction. The carriage comprises a torque input member for receiving a torque from the driving unit and for moving the carriage in the conveyance direction. The carriage further comprises a carriage coupling means for connecting carriages such that the torque received from the driving unit by one of the carriages on the conveyance path can be transmitted to the succeeding carriages. The carriage coupling means separates the carriage from the succeeding carriage when this carriage moves from one linear path to the turning path. The carriage coupling means also couples the separated carriage with the preceding carriage when the carriage moves from the turning path to another linear path.
According to a preferred embodiment, the carriage coupling means comprises at least a driving member and a driven member. The driving member preferably comprises of a rotatable cam on one carriage and the driven member comprises projections mounted on the adjacent carriage. The projections are spaced apart in the longitudinal direction of the carriages and are formed with corresponding cam surfaces so that the rotatable cam can be fitted into and withdrawn from an engaging space defined between the projections.
The cam surfaces of the projections preferably can transmit a force of the rotatable cam for moving substantially along the longitudinal direction of the carriage. The force is transmitted to the other carriage on which the driven member is mounted. The cam surfaces of the projections also can permit the rotatable cam to be fit into and withdrawn from the engaging space if the rotatable cam moves in a direction at an angle different from 0xc2x0 or 180xc2x0, preferably substantially normal to the longitudinal direction.
The carriage may further comprise a torque input member having a linear movement input member for transmitting the output of a linearly driving member of the endless conveyor to the carriage. The linear movement input member can be coupled detachably to the linearly driving member, and may comprise a chain mounted on the carriage. The torque input member also includes a turning movement input member for transmitting a torque of a turning member of the endless conveyor to the carriage for turning the carriage. The turning movement input member is detachably coupled to the turning member while the turning member is running, and may comprise a cam follower and a rotatable cam that is detachably engageable with the cam follower
According to the present invention, there is further provided a conveying mechanism for circulating the above-described carriages in a predetermined conveyance direction along an endless conveyance path. The conveyance path is comprised of a pair of substantially linear paths and turning paths connecting the opposite ends of the substantially linear paths. The conveying mechanism comprises at least one driving unit for driving the carriages, and preferably two driving units provided at the opposite ends of the conveyance path and between the substantially linear paths. More particularly, a plurality of the carriages may be connected into coupling units that extend along the linear paths. The driving units comprise turning means for separating the carriages at downstream ends of coupled units and turning them along the turning paths. The conveying mechanism further includes linear movement output members that operate in synchronism with the turning means to convey the downstream ends of the coupled units to the turning means.
The coupled units can be formed by coupling a plurality of carriages in series, and the series of the carriages can be driven along the conveyance path by driving only some carriages. The carriage coupling means separates the carriage from the succeeding carriage when the carriage moves from one linear path to the turning path and couples the separated carriage with the preceding carriage when it moves from the turning path to another linear path. Only the carriages that are displacing from the linear paths to the turning paths can be separated from the coupled units. These carriages then are turned individually and can be coupled with the ends of the preceding coupled units after turning. Accordingly, the carriages can be circulated by providing only the pair of driving units at the opposite ends of the conveyance path and driving the downstream ends of the forward moving coupled unit and the returning coupled unit. As a result, the conveyance path can be changed relatively easily merely by changing the spacing between the pair of driving units and the number of the carriages that are coupled.
The conveying mechanism may comprise a plurality of base blocks arranged one after the other. The base blocks comprise path-defining means for defining the conveyance path on the base blocks. The conveyance path can be changed by changing the number of blocks. Thus, a change in specification can be accommodated easily merely by changing the number of the blocks. The blocks preferably are units that have lengths corresponding to stations.
The conveyance path preferably is formed on a table having a specified height. Thus the height of the carriages can be reduced as much as the height of the table, and the carriages can be smaller. Further, there is no possibility of damaging a floor surface and maintenance, such as cleaning, can be facilitated.
In the respective embodiments and modes described above, the carriages need not have the same specification. For instance, carriages having lengths at a ratio of 1:2 may be alternately arranged and conveyed to produce products having a plurality product numbers.